Conventionally, industrial control apparatuses called as programmable logic controllers (hereinafter, just referred to as PLCs) have been widely used as control apparatuses for controlling various target systems, such as a belt conveyor-type automatic assembling machine, in order to realize various control, for example, sequence control. Furthermore, a use of the plural PLCs in combination has been applied in recent years, as the target system has become more complicated.
Moreover, a display apparatus placed in a vicinity of the PLC is used for displaying data from each PLC or for giving control instructions to the PLCs. A programmable display apparatus, which is an HMI (Human Machine Interface) apparatus, is widely used as the display apparatus in recent years, instead of control panels for giving the control instructions to the PLCs, and display lamps for indicating working states of the PLCs. Apart from this, a control system is, in some cases, arranged such that the control system can be displayed or operated also by a control host computer located in a remote location remote from those display apparatus.
Specifically, for example, as shown in FIG. 44, PLCs 503 has a central role of controlling in a conventional control system 501. Each PLC 503 is connected to a control-object apparatus (an apparatus to be controlled) 521a and a sensor 521b of a target system 502, and a programmable display apparatus 505 for displaying and for giving control instructions. Further, the PLC 503 is connected to other PLCs 503 and a control host computer 507 via a serial cable 504. Sending and receiving of control data between the PLC 503 and the control host computer 507, and between the respective PLCs 503 are carried out by using a communication function of the PLCs 503.
In this arrangement, a display processor 571 of the control host computer 507 communicates with the PLC 503 to receive data that represents a state of the target system 502, then displays a screen in accordance with the state, and sends the control data to the PLC 503 in accordance with input by a user. The target system 502 is controlled in accordance with the control data. Similarly, the programmable display apparatus 505 displays/controls the state of the target system 502, while communicating with the PLC 503.
The above arrangement, however, requires that the screen for the display processor 571 of the control host computer 507 be generated, besides a screen for the programmable display apparatus 505. This arises not only a problem that the generation of the screen is necessary but also a problem that the control host computer 507 cannot check the screen displayed on the programmable display apparatus 505.
Specifically, the programmable display apparatus 505 carries out displaying/controlling in accordance with screen data. The screen data is composed by combining information, where a unit of information is information that represents corresponding relationship between positional information for specifying an area on a base screen, and an address of a device that corresponds to a display or input onto the area. The screen, data is generated by an image processor 572 of the control host computer 507, and then is delivered to each programmable display apparatus 505.
Moreover, the control system 501, which is basically a closed system, does not allow seeing the state of the control system, such as the screen of the programmable display apparatus, from a remote location. Arts of seeing states of control apparatuses and the like via the Internet from a remote location are disclosed, for example, in U.S. Pat. No. 5,805,442 (Grant date: Sep. 8, 1998), International Patent Publication No. WO 99/13388 (published on Mar. 18, 1999), and International Patent Publication No. WO 99/13418 (published on Mar. 18, 1999). However, the above problem cannot be solved even by the arts of the Patents.
On the other hand, since the control host computer 507 has different usage and a different installation location from those of the programmable display apparatus 505, the control host computer 507 and the programmable display apparatus 505 are different from each other in terms of (a) hardware arrangements, such as CPUs and memory maps and (b) software arrangements, such as operating systems. Therefore, the display processor 571 cannot display/control in accordance with the screen data of the programmable display apparatus 505. Thus, the display processor 571 generates a display-use screen of its own. Moreover, it is necessary to go to the installation location of the programmable display apparatus 505 in order to check display contents of the programmable display apparatus 505.
A control program specifies the action of the PLC 503. For this reason, for example, before starting the PLC 503 to operate, or at a time the PLC 503 is corrected for inconvenience, a new control program is generated (corrected) by control program generating software and the like, which is installed in the control host computer 507. The control program is delivered to the PLC 503 via the serial cable 504.
In the control system 501, for updating the control program, a programmer of the control program needs to go near to the control host computer 507 and the PLC 503 so as to operate the control host computer 507 connected to the PLC 503. This arises a problem that updating of program is troublesome.
Furthermore, because the PLCs 503 have been developed from the sequencer, in most cases, different manufacturers use different communication protocols for data communication. Sometimes, different types of PLCs of the same manufacturer use different communication protocols for data communication. Further, because each type of the PLCs 503 uses a different CPU and address map, it is necessary to generate a control program for each type of the PLCs 503. Therefore, the generation (correction) of the control program requires, for each type of PLCs, control program generating software that corresponds to the type of PLCs.
On the other hand, each control program generating software is, as shown in FIG. 44, so arranged that the control program be outputted directly to the PLC 503 via the serial cable 504. Therefore, most of the types of the control program generating software have no function to update the control program from a remote location. However, it is very troublesome to generate new control program generating software that has the function to update the control program of the PLCs 503 from a remote location. Specifically, the control program generating software is sold as a separate application package, in most cases. Therefore, a request of the control program generating software generally goes to a selling agency of the application package.
Moreover, a relatively complicated process is carried out in the control program software because the control program is generated, for example, from a ladder diagram. As a result, it is troublesome to generate new control program generating software, besides the application package. In addition, it is necessary to correct or newly generate the control program generating software for each type of the PLCs, since different types of PLCs use different control programs. Therefore, both of correcting and newly generating of the control program generating software are unrealistic.